I've got the iPod Pioneer adaptor in my Clio and it's really good. Only cost £50.00 from Halfords and is so much better than the radio adaptors you can buy. I've also got the Griffin iPod adaptor which I no longer use and bought it off Ebay with a car charger for about £25.00 delivered from Canada.
In fairness, the radio adaptors are okay, given that they can be used with your existing head unit, but the sound quality is noticeably better with a proper adaptor like the Alpine of Pioneer ones.